Hole arrangement of liners of a combustion chamber of a gas turbine engine with low combustion dynamics and emissions

ABSTRACT

A gas turbine combustion chamber with an inner housing and an outer housing the inner housing having an inner wall element with a first hole arrangement and a second hole arrangement is provided. The inner wall element envelopes a burner volume. The first hole arrangement has first holes arranged in a first areal density, the second hole arrangement has second holes arranged in a second areal density. The outer housing has an outer wall element with a further first hole arrangement and a further second hole arrangement. The outer wall element of the outer housing envelops the inner wall element of the inner housing so that a gap in between is formed. The further first hole arrangement has further first holes arranged in a further first areal density, the further second hole arrangement has further second holes arranged in a further second areal density.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2012/074459 filed Dec. 5, 2012, and claims the benefitthereof. The International Application claims the benefit of EuropeanApplication No. EP 12161509 filed Mar. 27, 2012. All of the applicationsare incorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a housing for a combustion chamber fora gas turbine and to a method for producing a combustion chamber of agas turbine.

ART BACKGROUND

In a field of gas turbine technology it is an aim to reduce theproduction of environmental pollutants such as various oxides ofnitrogen (NOx), carbon monoxide (CO) and unburned hydrocarbons (UHC).Therefore, it is an aim to achieve a reliable and stable lean-burncombustion process in a combustion chamber of a gas turbine.

In order to provide a lean-burn combustion process more air is directedin particular close to the front end of the combustion chamber (wherethe combustion process is initiated) to be mixed with fuel in theburner. This is achieved by rebalancing the effective areas, that is theaccumulated hole area of the combustion can and that of the burner i.e.swirler. However, directing more air flow through the front end, thecombustion chamber promotes combustion instabilities which is aninherent problem associated with the lean-burn combustion.

In order to damp the combustion instabilities and in particular thecombustion dynamics inside the combustion chamber the wall elements ofthe combustion chamber housings are provided with holes through which agas exchange takes place.

GB 2 309 296 A discloses a gas turbine engine combustor wherein thecombustor comprises an inner combustor wall and an outer combustor wall.To the combustor wall damping holes are formed. The damping holes arearranged uniformly over the wall section, i.e. the damping holes havethe same distances between each other.

EP 1 104 871 A1 discloses a combustion chamber for a gas turbine engine,wherein the combustion chamber is a twin wall combustion chamber. Aninner wall and an outer wall of the twin wall combustion chambercomprise effusion holes in order to provide an impingement cooling. Theeffusion holes are uniformly distributed over the effective inner wallor outer wall.

EP 1 321 713 A2 discloses an improved flame tube of a combustion chamberof a gas turbine. Cooling air is guidable through apertures of therespective walls of the flame tube.

SUMMARY OF THE INVENTION

It may be an object of the present invention to provide a combustionchamber with reduced combustion instabilities and lower emissions.

This object may be solved by a housing for a combustion chamber for agas turbine, by a combustion chamber for a gas turbine and by a methodfor producing a combustion chamber for a gas turbine according to theindependent claims.

According to a first aspect of the present invention a housing for acombustion chamber for a gas turbine is presented. The housing comprisesa wall element which comprises a first hole arrangement and a secondhole arrangement. The first hole arrangement comprises first holesthrough which first holes fluid is streamable. The first holearrangement further comprises a first areal density of the first holes.The second hole arrangement comprises second holes through which secondholes fluid is streamable. The second hole arrangement further comprisesa second areal density of the second holes. The first areal densitydiffers from the second areal density.

According to further aspects of the present invention a combustionchamber for a gas turbine is presented. The combustion chamber comprisesan inner housing which comprises the features of the above describedhousing and an outer housing which may also comprise the features of theabove described housing. The outer wall element of the outer housing atleast partially envelopes the inner wall element of the inner housingsuch that a gap between the inner wall element and the further outerwall element is formed.

The terms “inner” and “outer” relate to a relative position i.e. of theinner and outer wall elements with respect to the distance between thewall element and the flame volume in the combustion chamber. The centeraxis of the combustion chamber may be a symmetry line of a (e.g.cylindrically formed) combustion chamber (such as a can-type combustionchamber), i.e. passing though the flame region or it may be for exampleparallel or even coincide with the rotor centre line of the gas turbine(such as an annular combustion chamber).

According to a further aspect of the present invention a method forproducing a combustion chamber of a gas turbine is presented. Accordingto a method, a first hole arrangement which comprises first holes isformed into an inner wall element of an inner housing, wherein throughthe first holes fluid is streamable and wherein the first holearrangement comprises a first areal density of the first holes.Further-more, according to the method, a second hole arrangement whichcomprises second holes is formed into the inner wall element, whereinthrough the second holes fluid is streamable and wherein the second holearrangement comprises a second areal density of the second holes. Thefirst areal density differs from the second areal density.

The term “areal density” (surface density) defines the number of holesper unit area. If, for example, two adjacent hole arrangements comprisea different areal density, each of the adjacent hole arrangementcomprise a different number of holes. This results in a non-uniformdistribution of holes over the respective hole arrangements.

Hence, by an embodiment of the present invention a wall element of ahousing for a combustion chamber comprises the first hole arrangementwith the first areal density and the second hole arrangement with thesecond areal density. Hence, the holes of a wall element are distributednon-uniformly and are particular adapted to respective flowcharacteristics of a respective fluid which flows along the wallelement.

The housing for a combustion chamber of a gas turbine may be an innerhousing which surrounds for example the combustion volume of thecombustion chamber. The housing may further be an outer housing whichpartially surrounds the inner housing. Hence, by applying an innerhousing and an outer housing, a twin-walled or double-walled combustionchamber (i.e. a double skin liner) may be formed. A gap may existbetween the inner housing and the outer housing. A fluid, e.g. a coolingfluid/gas, which streams along the outer wall element, may enter throughthe first and second holes of the outer wall element into the gap forcooling purposes. The fluid may further flow from the gap through thefirst and second holes of the inner wall element into the combustionspace of the combustion chamber for cooling purposes.

The inner wall of the inner housing of a double skin liner envelopes aburner volume of the combustion chamber. Around the inner housing andconsequently around the burner volume, an outer wall of an outer housingsurrounds the inner wall of such the double skin liner in such a waythat a gap is pro-vided. Consequently, the gap also surrounds the burnervolume. A cooling fluid stream is streamable through the respectiveholes of the outer wall into the gap. The cooling fluid streams furtherfrom the gap between the two wall elements through the holes of theinner wall into the burner volume of the combustion chamber.

Hence, by a conventional approach of combustion chambers, holes of wallelements of housings for combustion chambers are distributed uniformly.In conventional approaches, the first hole arrangement and second holearrangement comprise one and the same areal density of the respectiveholes. According to the present inventive approach of aspects of thepresent invention the holes are distributed non-uniformly in the (innerand outer) housing of the combustion chamber. Thereby, the distributionof the holes may be adapted and customized to the flow parameters of the(burned) fluid of the combustion chamber and to the flow parameters ofthe cooling gas.

Thereby, the combustion dynamics inside the combustion chamber may bereduced. Hence, a longer life of the housing and other combustioncomponents results due to e.g. the reduction of fluctuation in thetemperature profile at the wall elements. Furthermore, by the reducedcombustion dynamics of the wall sections, the turbine efficiency and theoperating temperature of the turbine may be increased without affectingthe life of the housing of the combustion chamber. Hence, also thenitrogen (NOx) emissions may be reduced for example by operating the gasturbine with a lean-burn combustion, i.e. by a lower pilot fuel splitinside the gas turbine. Summarizing, the distribution of the holes in anon-uniform manner and by arranging the pattern of the holes in arespective hole arrangement the combustion chamber may operate at lowernitrogen (NOx) emissions because for example more air may be fed to thecombustion process for providing a lean-burn combustion. Furthermore,the flame temperature is reduced due to the lean-burn combustion.

According to a further exemplary embodiment, the wall element is formedfor at least partially extending along a circumferential directionaround the central axis of the combustion chamber. Generally, thecombustion chamber is formed cylindrically (or conically). The centralaxis forms e.g. the symmetry axis of the combustion chamber, forexample. According to a further exemplary embodiment, the first holes ofthe first hole arrangement are formed into the wall element one afteranother along the circumferential direction for forming at least onefirst row of the first holes.

According to a further exemplary embodiment, the second holes of thesecond hole arrangement are formed into the wall element one afteranother along the circumferential direction for forming at least onesecond row of second holes. The amount of first holes are equal forexample to the amount of the second holes seen over the wholecircumference, but the areal density for each row of holes variesbetween the first and second rows of holes.

According to a further exemplary embodiment, the second holes of thesecond hole arrangement are formed into the wall element one afteranother along the circumferential direction for forming at least onesecond row of second holes. Because the first holes in the first holearrangement comprise a first areal density which differs from the secondareal density of the second holes of the second hole arrangement, theamount of first holes differs for example to the amount of the secondholes.

Regarding the above described exemplary embodiments comprising the firstrow and the second row, the amount of first rows differs from the amountof second rows. Additionally or alternatively, the amount of first holesin the first row differs from an amount of second holes of a second row.This results in a first areal density, which differs from the secondareal density, and thus in a non-uniform distribution of first andsecond holes along the wall element.

According to a further exemplary embodiment, the first holes of thefirst hole arrangement are formed into the wall element one afteranother along a first direction. The first direction differs from thecircumferential direction for forming at least one further first row offirst holes.

In particular, according to a further exemplary embodiment, the firstangle between first direction and the circumferential direction isbetween approximately 10° and approximately 80°, in particular betweenapproximately 30° and approximately 60°. Hence, the first holes arearranged into the wall element such that the further first row runs in aspiral way along the respective (e.g. tubular) wall element.

According to a further exemplary embodiment, the second holes of thesecond hole arrangement are formed into the wall element one afteranother along a second direction. The second direction differs from thecircumferential direction and/or from the first direction for forming atleast one further second row of the second holes.

In particular, according to a further exemplary embodiment, the secondangle between the second direction and the circumferential direction isbetween approximately 10° and approximately 80°, in particular betweenapproximately 30° and approximately 60°. By the further first row andthe further second row, the respective first and/or second holes areformed one after another along a respective first and second directionssuch that the respective further first row and the respective furthersecond row may form a helical (i.e. spiral) run around the centre axisalong the wall element.

According to a further exemplary embodiment of the method, an outer wallelement of an outer housing is arranged with respect to the inner wallelement such that the outer wall element at least partially envelopesthe inner wall element and such that a gap between the inner wallelement and the outer wall element is formed.

According to a further exemplary embodiment of the method, a furtherfirst hole arrangement is formed into the outer wall element, whereinthe further first hole arrangement comprises further first holes throughwhich further first holes a further fluid (e.g. cooling fluid/gas) isstreamable. The further first hole arrangement comprises a further firstareal density of the further first holes. Furthermore, a further secondhole arrangement which comprises further second holes is formed into theouter wall element, wherein through the further second holes a furtherfluid (e.g. cooling fluid/gas) is streamable, wherein the further secondhole arrangement comprises the further second areal density of thesecond holes. The further first areal density differs from the furthersecond areal density.

The total hole area for the inner and or outer wall is distributed overthe wall such that bands or areas of different hole density emerges. Thecriteria for the distribution depend on the flow parameters which may befor example the temperature, the flow velocity, the flow directionand/or the turbulence of the fluid and/or a further fluid.

Hence, by the above described method, the arrangement of the first holesand the second holes are designed and formed while taking into accountthe flow parameters of the respective fluid. Hence, an effective holedistribution of the holes and hence an improved guidance of the fluidand the further fluid along the respective wall elements is provided.Thereby, also the efficiency of the combustion chamber due to theadapted hole arrangement is achieved.

For example, holes of hole arrangements in a wall element may be at thebeginning of the method equally distributed and hence comprise an equalareal hole density. Next, some of the holes may be removed from theexisting hole arrangements, such that a non-equal distribution and anon-equal hole density between the respective hole arrangements areformed. Next, it is measured how the total hole area is reduced in aflow test as confirmation. Next, it is calculated how to ma-chine andarrange the respective holes to get the nominal flow parameters and toachieve a good damping characteristic. Next, the respective holes aredistributed in the respective hole arrangements, so that an unevendistribution and/or an uneven areal density of holes is formed, in orderto match up with calculated nominal flow parameters and the totaleffective flow area for the combustion chamber, respectively.

By the above described invention, combustion dynamics of the fluidinside the combustion chamber may be reduced. In other words, the innerwall elements and the outer wall elements are perforated with holes in anon-uniform and customized manner. Hence, due to the reduction of thecombustion dynamics, the lifetime for the combustion chamber componentand the downstream located turbine stage components as a result ofreduced flame fluctuations and temperature profiles is achieved.Furthermore, the NOx emissions are reduced, because due to the reducedcombustion dynamics a lower pilot fuel split (pilot fuel [pilotfuel+main fuel]) may be applied.

It has to be noted that embodiments of the invention have been describedwith reference to different subject matters. In particular, someembodiments have been described with reference to apparatus type claimswhereas other embodiments have been described with reference to methodtype claims. However, a person skilled in the art will gather from theabove and the following description that, unless otherwise notified, inaddition to any combination of features belonging to one type of subjectmatter also any combination between features relating to differentsubject matters, in particular between features of the apparatus typeclaims and features of the method type claims is considered as to bedisclosed with this application.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects defined above and further aspects of the present inventionare apparent from the examples of embodiment to be described hereinafterand are explained with reference to the examples of embodiment.Embodiments of the invention will be described in more detailhereinafter with reference to examples of embodiment but to which theinvention is not limited.

FIG. 1 shows a housing of a combustion chamber with first and secondrows of holes according to an exemplary embodiment of the presentinvention;

FIG. 2 shows a housing of a combustion chamber with first and secondrows of holes according to an exemplary embodiment of the presentinvention;

FIG. 3 and FIG. 4 show abstract views of hole patterns in a respectivehousing of a combustion chamber according to an exemplary embodiment ofthe present invention;

FIG. 5 shows a schematical view of a combustion chamber comprising aninner housing and an outer; and

FIG. 6 shows a schematical view of a method for producing a housingaccording to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The illustrations in the drawings are schematical. It is noted that indifferent figures, similar or identical elements are provided with thesame reference signs.

FIG. 1 shows a housing for a combustion chamber 100 for a gas turbine.The housing comprises a wall element 101 which comprises a first holearrangement I and a second hole arrangement II. The first holearrangement I comprises first holes 110 through which first holes 110fluid is streamable. The first hole arrangement I comprises a firstareal density of the first holes 110.

The second hole arrangement II comprises second holes 120 through whichsecond holes 120 fluid is streamable. The second hole arrangement IIcomprises a second areal density of the second holes 120.

The first areal density differs from the second areal density. That isthat the amount of first holes 110 per area unit differs from the amountof second holes 120 per area unit. In other words, the first holes 110are distributed with a different pattern and/or with a different amountand/or with a different size (e.g. hole diameter) with respect to thesecond holes 120 in the second hole arrangement II.

For example, as can be taken from FIG. 1, the first hole arrangement I,the second hole arrangement II and for example a third hole arrangementIII comprise the same areal size. Furthermore, the first holearrangement I, the second hole arrangement II and the third holearrangement III may define the areal unit which may define therespective first, second and/or third areal density of the holes.

In FIG. 1, the density of the first holes 110 within the first holearrangement I is higher than the second areal density and third arealdensity of the respective second hole arrangement II and third holearrangement III, respectively.

More holes may be arranged at the upstream front end of the wall element101 because this is where the flame is located. For example asexemplarily shown in FIG. 1, the first hole arrangement I may have threefirst rows 111, the more downstream located second hole arrangement IImay have two second rows 121 and the farther downstream located thirdhole arrangement III may have one third row 131.

In particular, as shown in FIG. 1, the combustion chamber 100 comprisesa burner section 104 (e.g. a front end section) at an upstream locationof the combustion chamber 100 with respect to a flow direction of thefluid along the central axis 102 of the combustion chamber 100. At thedownstream end of the combustion chamber 100 with respect to a flowdirection of the fluid along the central axis 102 the combustion gasexits the combustion chamber 100 and flows further to the turbine stagesof the gas turbine, for example. As can be taken from FIG. 1, the arealdensity of the respective holes 110, 120, 130 decreases from theupstream end to the down-stream end of the combustion chamber 100. Bythe exemplary distribution of the holes 110, 120, 130 in FIG. 1, thefirst holes 110 of the first hole arrangement I are formed into the wallelement 101 one after another along a circumferential direction 103 forforming first rows 111 of the first holes 110. Adjacent to the firstrows 111 and along the downstream direction, the second holes 120 of thesecond hole arrangement II are formed into the wall element 101 oneafter another along the circumferential direction 103 for forming e.g.two second rows 121 of second holes 120. Furthermore, as shown in FIG.1, the third holes 113 of the third hole arrangement III are formed intothe wall element 101 one after another along the circumferentialdirection 103 for forming at least three third rows 131 of the thirdholes 130.

For example, if the respective hole arrangement I, II, III comprise thesame defined area, the amount of holes 110, 120, 130 and the amount ofrows 111, 121, 131 decrease along the direction from the upstream end ofthe combustion chamber 100 to the downstream end of the combustionchamber 100. In other words, the distance between the two second rows121 is smaller than the distance between the third rows 131, forexample. For example, the distance between the first rows 121 at anupstream end of the combustion chamber 100 may be half of the distancebetween the third rows 131 at the downstream section of the combustionchamber 100.

In FIG. 1, the hole arrangement I, II, III as shown in FIG. 1 may beapplied to an inner wall element 501 (see FIG. 5) (inner liner). Due tothe non-uniform hole distribution along the central axis 102 from anupstream end of the combustion chamber 100 to a downstream end of thecombustion chamber 100 the areal density at the downstream part is lowerthan the areal density of the holes at an upstream part of thecombustion chamber. Furthermore, also a proper effusion cooling inparticular at the upstream part of the wall element 101 compared to auniform arranged hole arrangement is achieved. Furthermore, by the holedistribution as shown in FIG. 1 proper damping characteristics of thecombustion dynamics within the combustion chamber 100 is achieved. Thearrangement of the axial rows 111, 121, 131 results on the basis of adesired reduction of the combustion chamber effective area and a desiredmass flow of the cooling fluid through the respective holes 110, 120,130 through the inner wall, respectively.

FIG. 2 shows the combustion chamber 100, wherein the wall element 101comprises the first hole arrangement I and the second hole arrangementII. The first holes 110 of the first hole arrangement I are formed intothe wall element 101 one after another along a first direction 201. Thefirst direction 201 differs from the circumferential direction 103 forforming at least one further first row 211 of first holes 110.

Additionally or alternatively the second holes 120 of the second holearrangement II are formed into the wall element 101 one after anotheralong a second direction 202. The second direction 202 differs from thecircumferential direction 103 for forming at least one further secondrow 221 of second holes 120.

As can be taken from FIG. 2, the further first rows 211 may comprise forexample two first holes 110. The further second row 221 comprises forexample three second holes 120. Hence, the areal density of the secondholes 120 in the second hole arrangement II is higher than the arealdensity of the first holes 110 in the first hole arrangement I.

Furthermore, as shown in FIG. 2, by arranging the respective holes 110,120 along the first and second direction, a helical (spiral) run aroundthe center axis 102 along the wall element 101 is formed. In otherwords, the respective holes 110, 120 in FIG. 2 are arranged in adiagonal manner (in a spiral pattern) with respect to thecircumferential direction 103.

In particular, the housing comprising the hole pattern as shown in FIG.2 may be applied for an outer housing with an outer wall element 502(see FIG. 5). In particular, the first direction and the seconddirection of the diagonal further first rows 211, 221 may be in the samedirection as a spiral and helical motion of the combustion gases insidethe combustion chamber 100. Furthermore, the spacing between twoadjacent diagonal further rows 211, 221 may either be uniform ornon-uniform along the circumferential direction 103, depending on therequired flow parameters through the respective holes 110, 120, 130.

A combustion chamber 100 which comprises the inner housing shown in FIG.1 and the outer housing shown in FIG. 2 has the surprising effects ofefficient cooling properties, efficient damping of flame dynamics andstable flame characteristics in the combustion chamber.

FIG. 3 shows a more abstract view of the hole pattern as shown in FIG.2. In FIG. 3 in particular a hole pattern of an outer wall 502 (see FIG.5) of an outer housing of the combustion chamber 100 is shown. In FIG. 3exemplarily the first hole arrangement I and the second hole arrangementII are shown. The first holes 110 are arranged one after another longfurther first rows 211. The further first rows 211 extend along thefirst direction 201. Between the first direction 201 and thecircumferential direction 103, the first angle oil is defined.

The second holes 120 are arranged in the second hole arrangement II oneafter another along the second direction 202 and form the further secondrows 221. Between the second direction 202 and the circumferentialdirection 103 the second angle 2 is defined.

As shown in FIG. 3, the further first rows 211 and the further secondrows 221 have a spiral (diagonal) run with respect to thecircumferential direction 103. In particular, as shown in FIG. 3, alongthe circumferential direction 103 the distance between the respectivefurther rows 211, 221 are different between each other. For example, asshown in the first hole arrangement I, the first hole arrangement Icomprises three pairs of further first rows 211, wherein between eachpair of further first rows 211 a larger distance exists than betweeneach of the two further first rows 211 which defines a respective pairof further first rows 211.

In comparison to that, as shown in the second hole arrangement II, thesecond hole arrangement II comprises two pairs of further second rows221 and one further second row arrangement comprising three furthersecond rows 221.

Hence, along the circumferential direction, the distance between eachfurther row 211, 221 vary such that a non-uniform distribution of holes110, 120 is provided.

FIG. 4 shows an abstract view of a hole pattern as shown inschematically in FIG. 1. In particular, a hole pattern shown in FIG. 4may be beneficial when being applied to an inner wall 501 (see FIG. 5)of an inner housing of the combustion chamber 100. First rows 111 offirst holes 110 and second rows 121 of second holes 120 are arranged oneafter another along the axial direction 102, wherein the first rows 111and the second rows 121 are parallel with respect to the circumferentialdirection 103. The distance between the first rows 111 in the first holearrangement I are smaller than the distances between the second rows 121of the second hole arrangement 11.

FIG. 5 shows for a better overview a cross-section of a double wall cantype of combustion chamber 100. An inner wall 501 of an inner housingenvelopes a burner volume of the combustion chamber 100. Around theinner housing, an outer wall 502 of an outer housing surrounds the innerwall 501 in such a way that a gap is provided. A cooling fluid stream503 is streamable through the respective holes 110, 120 of the outerwall 502 into the gap. The cooling fluid stream 503 form at least a partof the cooling fluid stream 504 streaming from the gap between the twowall elements 501, 502 through the holes of 110, 120, 130 of the innerwall 501 into the combustion chamber 100. The cooling fluid stream 504may be smaller or greater than the cooling fluid stream 503 depending onif cooling fluids has been added or removed in the gap between the twowall elements 501 and 502.

As shown in FIG. 5, the inner wall 501 and the outer wall 502 surroundthe center axis 102 and thereby form a tubular shaped section of thecombustion chamber 100.

FIG. 6 shows a method of calibrating and arranging a desired holearrangement I, II, III of an inner wall element 501 and an outer wallelement 502. In step 601, the initial combustion chamber design isdefined. The initial combustion chamber design may comprise an uniformor non-uniform distributed hole pattern in the inner wall element 501and/or in the outer wall element 502.

Next, the combustion chamber is operated, measured or analysed undernominal operating conditions such that the inner wall element 501 andthe outer wall element 502 are exposed to the cooling fluid stream 503and to the further cooling fluid stream 504, respectively. The coolingfluid flows with its respective operating flow parameter through therespective holes of the inner wall element 501 and outer wall elements502.

Next, in step 602, the hole arrangements I, II, III of the inner wallelement 501 is decided. The effective area of the inner wall element 501is determined by the total number of holes 110, 120, 130 of the innerwall element 501. Similarly, in step 603, the hole arrangements I, II,III of the outer wall element 502 is decided. The effective area of theouter wall element (outer liner) 502 is determined by the total numberof holes 120, 130, 140 on the wall of the outer wall element 502.

Next, in step 605, the total combustion chamber 100 effective area isdetermined on a basis of the hole arrangements I, II, III of the innerwall element 501 and the hole arrangements I, II, III of the outer wallelement 502.

Furthermore, the flow parameters of the fluid (e.g. the velocity of thefurther cooling fluid stream 504) exiting the inner wall element 501into the combustion space of the combustion chamber 100 is determined(see step 604).

Next, in step 606, the determined value of the flow parameters of thecooling fluid 503, 504 and the geometric parameter of the combined innerand outer wall elements 501, 502 (i.e. the combustion chamber 100) arecompared to nominal values of e.g. velocity of the cooling fluid 503,504 and the effective area of the combustion chamber 100.

If the measured flow parameters and/or the nominal value of thegeometric parameter of the combustion chamber 100 do not correspond tothe respective nominal values, in step 607, the first areal density, thefurther first areal density, the second areal density and/or the furthersecond areal density of the respective holes in the inner wall element501 and/or the outer wall element 502 and thus the respective holepattern is individually amended until the nominal values of theflowgeometric parameters are reached.

If the nominal values are achieved, the final design of the hole patternof the inner wall element 501 and the outer wall element 502 is achieved(see step 608).

Hence, by the above described method as shown in FIG. 6, a customizedand optimized wall pattern of the inner wall element 501 and the outerwall element 502 is achieved under real operating conditions of thecombustion chamber, so that an optimized fluid flow and an effectivecombustion chamber 100 is designed. In conventional approaches, the holepattern is calculated and distributed equally over a given surface. Bythe present approach, the hole pattern within the given surface aredetermined balancing the requirements on damping with that ofdistributing cooling air over a surface using an iterative process asshown in FIG. 6 and as described above. In other words, the holepatterns are customized to the operating conditions of the combustionchamber 100 and the gas turbine to which the combustion chamber 100 ismounted.

For sake of clarity, not all holes 110, 120, 130, and rows 111, 121,131, 211, 221 are identified with a respective reference sign in theabove described figures.

It should be noted that the term “comprising” does not exclude otherelements or steps and “a” or “an” does not exclude a plurality. Alsoelements described in association with different embodiments may becombined. It should also be noted that reference signs in the claimsshould not be construed as limiting the scope of the claims.

1. A combustion chamber for a gas turbine, the combustion chambercomprising: an inner housing and an outer housing, wherein the innerhousing comprises an inner wall element which comprises a first holearrangement and a second hole arrangement, wherein the inner wallelement envelopes a burner volume of the combustion chamber, wherein thefirst hole arrangement comprises first holes through which first holesfluid is streamable, wherein the first holes are arranged in a firstareal density, wherein the second hole arrangement comprises secondholes through which second holes fluid is streamable, wherein the secondholes are arranged in a second areal density, and wherein the firstareal density differs from the second areal density, and wherein theouter housing comprises an outer wall element which comprises a furtherfirst hole arrangement and a further second hole arrangement, whereinthe outer wall element of the outer housing at least partially envelopsthe inner wall element of the inner housing such that a gap between theinner wall element and the outer wall element is formed, wherein thefurther first hole arrangement comprises further first holes throughwhich further first holes fluid is streamable, wherein the further firstholes are arranged in a further first areal density, wherein the furthersecond hole arrangement comprises further second holes through whichfurther second holes fluid is streamable, wherein the further secondholes are arranged in a further second areal density, and wherein thefurther first areal density differs from further the second arealdensity.
 2. The combustion chamber according to claim 1, wherein theinner wall element extends along a circumferential direction around acentral axis of the combustion chamber, and/or wherein the outer wallelement extends along the circumferential direction around the centralaxis of the combustion chamber.
 3. The combustion chamber according toclaim 1, wherein the inner wall element extends along a circumferentialdirection around a central axis of the gas turbine, and/or wherein theouter wall element extends along the circumferential direction aroundthe central axis of the gas turbine.
 4. The combustion chamber accordingto claim 2, wherein the first holes of the first hole arrangement areformed into the inner wall element one after another along thecircumferential direction for forming at least one first row of firstholes, and/or wherein the further first holes of the further first holearrangement are formed into the outer wall element one after anotheralong the circumferential direction for forming at least one furtherfirst row of further first holes.
 5. The combustion chamber according toclaim 2, wherein the second holes of the second hole arrangement areformed into the inner wall element one after another along thecircumferential direction for forming at least one second row of secondholes, and/or wherein the further second holes of the further secondhole arrangement are formed into the outer wall element one afteranother along the circumferential direction for forming at least onefurther second row of further second holes.
 6. The combustion chamberaccording to claim 2, wherein the first holes of the first holearrangement are formed into the inner wall element one after anotheralong a first direction, wherein the first direction differs from thecircumferential direction for forming at least one further first row offirst holes, wherein the further first holes of the further first holearrangement are formed into the outer wall element one after anotheralong a further first direction, wherein the further first directiondiffers from the circumferential direction for forming at least onefurther outer first row of further first holes.
 7. The combustionchamber according to claim 6, wherein a first angle between the firstdirection and the circumferential direction is between 10° and 80°,and/or wherein a further first angle between the further first directionand the circumferential direction is between 10° and 80°.
 8. Thecombustion chamber according to claim 2, wherein the second holes of thesecond hole arrangement are formed into the inner wall element one afteranother along a second direction, wherein the second direction differsfrom the circumferential direction for forming at least one furthersecond row of second holes, and/or wherein the further second holes ofthe further second hole arrangement are formed into the outer wallelement one after another along a further second direction, wherein thefurther second direction differs from the circumferential direction forforming at least one further outer second row of further second holes.9. The combustion chamber according to claim 8, wherein a second anglebetween the second direction and the circumferential direction isbetween 10° and 80°, and/or wherein a further second angle between thefurther second direction and the circumferential direction is between10° and 80°.
 10. A method for producing a combustion chamber for a gasturbine, the method comprising: forming a first hole arrangementcomprising first holes into an inner wall element of an inner housing ofthe combustion chamber, wherein through the first holes fluid isstreamable, wherein the first holes are arranged in a first arealdensity, and forming a second hole arrangement which comprises secondholes into the inner wall element, wherein through the second holesfluid is streamable, wherein the second holes are arranged in a secondareal density, wherein the first areal density differs from the secondareal density, and wherein the inner wall element envelopes a burnervolume of the combustion chamber, arranging an outer wall element of anouter housing of the combustion chamber with respect to the inner wallelement such that the outer wall element at least partially envelops theinner wall element and such that a gap between the inner wall elementand the outer wall element is formed, forming into the outer wallelement a further first hole arrangement which comprises further firstholes through which further first holes a further fluid is streamable,wherein the further first holes are arranged in a further first arealdensity, and forming into the outer wall element a further second holearrangement which comprises further second holes through which furthersecond holes further fluid is streamable, wherein the further secondholes are arranged in a further second areal density, wherein thefurther first areal density differs from the further second arealdensity.
 11. The method according to claim 10, wherein the methodfurther comprises: streaming the fluid stream through the first holearrangement and the second hole arrangement, streaming the further fluidstream through the further first hole arrangement and the further secondhole arrangement, determining a flow parameter of the fluid streamand/or the further fluid stream, and amending the first areal density,the further first areal density, the second areal density and/or thefurther second areal density until the measured values of the flowparameter of the fluid stream and/or geometric parameter of thecombustion chamber comply with corresponding nominal values of the flowparameter and/or geometric parameter of the combustion chamber.
 12. Thecombustion chamber according to claim 7, wherein the first angle betweenthe first direction and the circumferential direction is between 30° and60°.
 13. The combustion chamber according to claim 7, wherein thefurther first angle between the further first direction and thecircumferential direction is between 30° and 60°.
 14. The combustionchamber according to claim 8, wherein the second angle between thesecond direction and the circumferential direction is between 30° and60°.
 15. The combustion chamber according to claim 8, wherein thefurther second angle between the further second direction and thecircumferential direction is between 30° and 60°.